During the manufacture and final assembly of commercial airplanes and the like, various airplane systems are functionally tested, including the braking system. One of the essential functional tests administered to the braking system of commercial airplanes is a test to measure the amount of force the operator or pilot must apply to the individual brake pedals to stop a taxiing airplane. This test is typically conducted measuring three parameters: brake pedal position in terms of degrees of rotation; brake pedal force in terms of pounds of force being applied to the pedal; and the hydraulic pressure delivered to the brakes as a result of the brake pedal position. In many airplanes, there are two brake pedals generally parallel to each other, with each pedal hinge mounted at its bottom near the cockpit floor. With the development of power assist brakes in airplanes and other vehicles large braking forces are available, which enables the operator to apply significantly more breaking force to the tires and wheels than would be capable manually. This large force can stop the tires from rotating and the resultant skidding can wear through the tire carcass causing the tire to flat spot and possibly blow out. Thus, various industries such as the automobile industry have employed a biasing element, such as a spring, in the pedal circuit to give the operator a sense of how much braking force is being applied to the wheels and tires when the operator depresses the pedal.
Commercial airplanes, however, unlike automobiles, employ two brake pedals and can have 3000 psi available for braking, which can cause failure of the tires and wheels of the airplane if the application of the breaking force is not controlled. Therefore, as the operator or pilot depresses the brake pedals and the pedals rotate to various positions, each position of the pedal has a resultant pedal push back force which corresponds to hydraulic pressure being applied at the brakes. This push back force indicates to the operator or pilot how much braking force is being applied to the tires.
Currently, the aforementioned testing of the pedal position is accomplished via a multi-step procedure which includes attaching instrumentation to each of the brake pedals. This instrumentation is commonly referred to as a load cell and provides a read out of the force, in terms of pounds, being applied to the pedals and it also indicates the position of the pedals in terms of degrees which corresponds to the applied braking force at the tires. Also, each load cell typically operates in conjunction with an electrical box which provides a readout for each parameter identified above.
Next, operator or pilot force or pressure is applied to the load cells and hence to the brake pedals. This is currently accomplished manually by employing a person, usually a functional test mechanic, to simulate a pilot manually depressing the load cells and thus the brake pedals of the commercial aircraft being tested. While pressure from the operators foot is applied to the load cells attached to the pedals, the functional test mechanic interprets the data displayed by the electrical boxes. The brake system then is adjusted accordingly.
The aforementioned testing procedure has drawbacks however, because the procedure can be time consuming in terms of man hours, requiring multiple people to perform the various tasks. The procedure is also physically demanding.
The pedal forces that are reproduced are typically around 80-90 pounds at the upper end, and the operator usually has to sustain this pressure for 2-3 minutes while the brake system is adjusted. This duration of time can approach ten minutes or longer, depending the type and extent of adjustment required. As a result, the operator oftentimes becomes fatigued and his or her legs begin to quiver, causing the values indicated on the electrical boxes to vary and become imprecise due to the application of inconsistent or non-constant foot pressure. The mechanic adjusting the brake pressure at the tires is then continually chasing the required values.
Accordingly, there is a need in the art to provide an apparatus and method that allows for the efficient, precise functional testing for pedal operated systems such as brake systems and the like, that is ergonomic and less fatiguing.